Nondimensional Load Capacity Research Articles

DESIGN OF POROUS STEP BEARING BY CONSIDERING DIFFERENT FERRO FLUID LUBRICATION FLOW MODELS

The aim of this article is to carry out analysis to enhance the performance of the ferro fluid lubricated porous step bearing. The porous coating is assorted to the lower flat impermeable surface. A step is there in upper surface which approaching to lower surface. This study considered that magnetic field is flexible and oblique to the lower surface. By considering Jenkins Model, expressions for pressure and load capacity are obtained. The non-dimensional load capacity is also calculated for various parameters. Based on results, it is observed that load capacity increases if suitable step size is considered. Also, comparison between R. E. Rosensweig Model and Jenkins Model is carried out. Finally, it is advised to design a porous step bearing, one should consider Jenkins Model over R. E. Rosensweig Model.

Analyzing Short Porous Hydrodynamic Journal Bearing Numerically Considering Micropolar Lubrication and Isotropic Roughness

In present days of high speed machines and machinery, the aim to reduce the energy loses becomes a major aspect of research for economic reasons and long-term reliability. It is known that an industrial nation can save about 1% of gross national product by better tribological exercises. Many modern machines use porous bearings for its ability to act as a lubricant reservoir. The lubricant used in the open adverse operating situations gets contaminated with worn-out particles and dust, and can be better studied by micropolar lubrication theory. Moreover, machined surfaces always have some degree of roughness which adds to the loss of energy. The present work aims at clubbing the effect of roughness in hydrodynamic lubrication using micropolar fluid with a thin porous bush assuming the velocity slip of lubricant film at the porous bush and fluid film junction. The governing equation for fluid pressure in the porous matrix and hydrodynamic film zone are developed following Darcy’s equation and hydrodynamic micropolar lubrication theory, considering Christensen’s stochastic model of roughness. The bearing is approximated as a short one. Modified Reynold’s equation is numerically solved to compute fluid film pressure in steady-state condition. Friction parameters and non-dimensional load capacity in terms of roughness parameters and porous bearing characteristics are presented in case of Newtonian and micropolar fluids.

Analysis of magnetohydrodynamic partial slip laser bump texture slider and journal bearing

A model of magnetohydrodynamic partial slip laser texture bearing (slider and journal) is developed. The influence of laser bump texture and slip laser texture partial configuration on the magnetohydrodynamic performance analysis of bearing is presented. An electrically conducting fluid is confined to bearing surfaces under uniform magnetic field perpendicular to slider bearing and inclined to the line of maximum film thickness to journal bearing. A one-dimensional analysis based on the narrow groove theory is considered to evaluate the nondimensional pressure distribution in bearing. Results of the nondimensional load capacity and coefficient of friction of magnetohydrodynamic partial laser bump texture and partial slip laser texture bearing configurations are analyzed. Partial slip configuration under MHD lubrication without laser bump texture brings in the performance improvement.

Analysis of Porous Layered Journal Bearing Lubricated with Ferrofluid

This paper presents an analysis of porous layered long journal bearing lubricated with ferrofluid using displaced infinitely long wire magnetic field model. The ferrofluid flow in the porous region is analyzed using modified Brinkman model. Nondimensional pressure and shear stress expressions are derived using Reynolds boundary conditions. Nondimensional load capacity and coefficient of friction are evaluated under the influence of permeability of porous media, porous layer thickness, lubricant layer thickness, magnetic field intensity and distance ratio parameter. A porous layered journal bearing lubricated with ferrofluid increases the load carrying capacity and reduces the coefficient of friction.

Analysis of Two-Layered Film Journal Bearing with Partial Slip Surface

Based on the approach of two-layered film consisting of different Newtonian viscosities, the present study examines the effects of partial slip bearing configuration on load capacity and friction coefficient for journal bearing. Navier slip boundary conditions are used to analyze partial slip configuration. A modified Reynolds equation for a journal bearing with two-layered film on a partial slip surface is presented. The modified Reynolds equation is derived taking into consideration of magnitude of lubricant layers film thickness, viscosities and the extent of partial slip on the bearing surface. The Reynolds boundary conditions are used in the analysis to predict nondimensional load capacity and coefficient of friction. Partial slip of bearing surfaces has a potential to improve load carrying capacity and reduce coefficient of friction for two-layered film journal bearing.

Analysis of Two-Layered Journal Bearing Lubricated with Ferrofluid

The present study investigates the load capacity and friction coefficient for a two-layered journal bearing lubricated with ferrofluid. A modified Reynolds equation for a two-layered ferrofluid is derived using displaced infinitely long wire magnetic field model. Reynolds boundary conditions are used to obtain nondimensional pressure and shear stress expressions. Nondimensional load capacity and coefficient of friction are analyzed under the influence of lubricant layer’s thickness, viscosities, magnetic field intensity and distance ratio parameter. Ferrofluid lubrication under the influence of magnetic field has potential to enhance load carrying capacity and reduce coefficient of friction for two-layered journal bearing.

Analysis of Nanoparticle Additive Couple Stress Fluids in Three-layered Journal Bearing

The present theoretical study investigates the load capacity and friction coefficient in a three-layered journal bearing lubricated with nanoparticle additive couple stress fluids. The couple stresses effects are analyzed based on Stokes micro-continuum theory. The nondimensional pressure and shear stress expressions are derived using modified Reynolds equation. The nondimensional load capacity increases and the coefficient of friction decreases using nanoparticle additive lubricants with couple stress effects. The three-layered journal bearing performance characteristics are improved with increase in both (i) surface adsorbent fluid film layer thickness and (ii) dynamic viscosity ratio of surface to core layer.

Load Capacity of Partially Textured Journal Bearing with Trapezoidal Recess

This work presents the load carrying capacity of partially textured journal bearing with trapezoidal recess. The partial texture geometry is composed of a number of successive cells of trapezoidal recess and land configurations. The non-dimensional pressure expressions for the partially textured journal bearing with trapezoidal recess are derived. Results of nondimensional load capacity are provided taking into consideration of texture geometry with trapezoidal recess and extent of partial texture.

물 정수압 저널 베어링의 이론적 해석

In this study, the nondimensional load capacity of water hydrodynamic journal bearings is calculated. A generalized coordinate formulation is applied to handle the complexity of bearing geometry. A window-based analysis program is developed to analysis the cylindrical hydrostatic bearings. Load capacities are calculated according to some design parameters such as clearance, diameter of orifice, size of recesses and temperature. The results are presented and discussed.

Effects of rarefaction on the characteristics of micro gas journal bearings

Given the definition of the reference Knudsen number for micro gas journal bearings, the range in the number is related to the viscosity of air at different temperatures. A modified Reynolds equation for micro gas journal bearings based on Burgdorfer’s first-order slip boundary condition is proposed that takes into account the gas rarefaction effect. The finite difference method (FDM) is adopted to solve the modified Reynolds equation to obtain the pressure profiles, load capacities and attitude angles for micro gas journal bearings at different reference Knudsen numbers, bearing numbers and journal eccentricity ratios. Numerical analysis shows that pressure profiles and non-dimensional load capacities decrease markedly as gas rarefaction increases. Attitude angles change conversely, and when the eccentricity ratio is less than 0.6, the attitude angles rise slightly and the influence of the reference Knudsen number is not marked. In addition, the effect of gas rarefaction on the non-dimensional load capacity and attitude angle decreases with smaller bearing numbers.

Characteristics of Micro Gas Journal Bearings Based on Effective Viscosity

According to the first order slip velocity boundary, a modified Reynolds equation for micro gas journal bearings is presented with consideration of effective viscosity under a rarefied flow condition. A modified Reynolds equation is attained and solved using the finite difference method. The nondimensional pressure, load capacity, and attitude angle for micro gas journal bearings under different reference Knudsen numbers (the ratio of ambient molecular mean free path to the average radial clearance), bearing numbers, and eccentricity ratios are obtained. The numerical analysis demonstrates that the slip model with effective viscosity is in a better agreement with the FK model derived by Fukui and Kaneko than that without effective viscosity. When the bearing number is constant, the pressure and load capacity decrease, and the attitude angle changes inversely with the increasing reference Knudsen number. The larger the eccentricity ratio, the larger change in attitude angle from effective viscosity. When eccentricity ratio is less than 0.6, the attitude angle changes softly, and the effect of effective viscosity is unobvious. When the eccentricity ratio is constant, the influence of effective viscosity on nondimensional load capacity and attitude angle becomes larger with the increasing bearing number, and the influence is more prominent with a larger reference Knudsen number.

Prediction of the coefficient of friction of a misaligned turbulent flow journal bearing

This paper offers computer solutions for a misaligned journal bearing operating in the turbulent regime. The modified Reynolds equation is solved numerically taking into consideration that the distribution of effective viscosity is dependent on local shear stress. The performance characteristics of finite hydrodynamic journal bearings are studied at various eccentricities for different degrees of misalignment up to a maximum value, which defines a journal bearing contact at one end. An empirical formula for the prediction of the coefficient of friction is established, in terms of the nondimensional load capacity and the degree of misalignment.